Romans 3:12

They have all turned aside, they are together become unprofitable; There is none that doeth good, no, not so much as one.

Because Israel did not understand and did not seek after God, they turned aside to follow foolish and hurtful things, even in many instances departing to follow after the gods of the pagans, thereby becoming unprofitable to God. All of the care and favor that God lavished upon them, with the intention that they should recognize and honor the Messiah when he came, and present him to the world - all that was lost. They were so unprofitable that they lost the key of knowledge, and far from recognizing and receiving the Lord when he at last came, they failed to recognize him, hated him, and murdered the Son of God! The profoundly adverse judgment of God in the perpetual hardening of that nation should always be considered against this background. They were to blame for not recognizing the Lord.